I have a 97 F150 4.6L with the automatic transmission and manual shift drive (4406 Transfer Case). I was having a problem with my overdrive and did a few test via Haynes manual and was able to determine that the OD switch was bad and replaced. All was well, when starting it was in OD and upon hitting the switch the OD light lit off and only switch gears 1 thru 3. It had continued to work well untill I ended up doing the TSB 97-13-21 for clunking in the drive shaft. I disconnected the VSS plug and the ground wire to the tail end of the transfer. I removed the six bolts of the tail according to the TSB but did not cut the the ground wire groument so that the tail could move more freely. I don't believe that anything was done during the repair but when it was completed I now have no functional OD switch. It is like it was before except when I turn the ignition on the off light flashes once before starting. My first question is this... What the hell is the ground wire running through the tail and back into the transfer case for? Second does this ground wire or the VSS wires have anything to do with the OD switch. I also would like to add that the fuse is ok. I also did a filter service on the transmission. Dropped the pan, replaced the filter and threw a jug of lucas in.... The TSB fixed the clunking but now I broke the Overdrive again. Any help at this point would be greatly appreciated. Sorry for the length but wanted to be as detailed as I can.... New to the forum and was hoping for some answer or some information to trouble shoot the overdrive on this truck...

 

Why not try grounding that wire that was disconnected to the frame, and see if it works? Seems like if it was working before and now it's not, something was undone during the repair. It's an easy place to start and I can't see how it would hurt.

 

As a point of information only, since I don't know what issues you now have.
The OD switch controls the PCM program only by switching a 12 volt source, command signal.
This causes the PCM to apply the OD function thru the trans control solenoids according the speed, engine power applied etc.
This means the OD switch does not directly control the transmission.
The OD switch wiring often developes a ground at the shift selectors area from movement rubbing thru the wire insulation and blows a fuse.

 

Guys thanks for the help so far but I can tell you I am only having the issue mention in the original post... When I checked the wiring before determining the TCS was bad I believe everything looked ok plus I have never blown any fuses for the TCS. What does not make sense is when turning the key to the on position the TCIL blinks on/off one time and then the pushing of the button never makes any change to either the light or transmisson shift changes. Now with this not working the transmission is still shifting fine just not able to kill fourth gear with the push of the TCS. I can tell you that the TCS and overdrive worked perfectly after replacing the switch and up to when I did the TSB, Transimssion drain/replace of filter and then a refill with Lucas and Mercon and last but not least a replacment of all four O2 Sensors. The filter change was only the removal of the tranny pan, then filter replacment and cleaning of the magent on the bottom of the pan. Bluegrass7/JB13290 can either one of you identify what the single ground wire going through the transfer case tail and into the back side of the transfer case is for? The only thing that was unplug during the TSB was the VSS two wire plug and the single wire ground? this plug is labeled G98G07170 and has four wire pins with only pin one(1) being used.... What is more frustrating is this was working fine after the initial repair and now somewhere along the way I have self inflicted more headaches... Can you guys point me in the right direction...

 

The TCS switch is powered from 12 volt supply thru a 5 amp fuse in the central fuse box.
The switch also is connected to the indicator lamp thru a resistor.
The switch signals the PCM for OD control.
The lamp is signaled from the PCM thru a seperate lead so it can signal a condition of off, on or a blinking condition for a trans issue. Since it blinks once or so means the power is there, and all of it's connectons are in place and good.
The blink is saying there is a problem. Normally if you turn the OD off (lamp lighted) and then restart the motor, it will be switched off again by the PCM, as a normal reset action.
.
The speed sensor is connected thru the digital trans range selector switch so the condition of use can be detected by the PCM.
Other side of sensor goes to the PCM for speed detection signals.
The trans is mounted in rubber mounts and can't be relied on for grounding without a seperate ground lead.
The tranfer case has a motor on it that also needs a reliable ground.
Revisit the harness plugs. Seems the issue should be simple somewhere in the work area. Anything against the exhaust and burned thru etc.

 

Bluegrass7,

I did some further testing and found that I do have continuity to the wire coming out of the transfer case so I can assume that I still have ground to plug G98G07170. What I could not determine is anything to the other side of the plug which ties into VSS harness and then I lose the wires above the transmission. And when I say anything that includes the following:

No Power with key off or on also there seems to be no continuity to the wire leading away from the transfer case. I was able to download from Mitchell One a circuit test TB for the TCS and TCIL which wen I have time will try to test the circuit. Let me know if there is anything else I can try... Thanks again